B2therandon

Hey guys, so I have a 98 base mustang, 5 speed. Runs Like a champ. But when I go to do a burnout it is only spinning the back right wheel. I was wondering if it's "easy" or even possible for me to swap the rear end with a gt to get the limited slip? Also.. I was looking on American muscle for performance parts and came across this tuner. http://americanmuscle.com/x3-custom-tuner-9698v6.html was wondering if anyone in here has had any experience with it? If so is there any notice in performance? I guess what I'm asking is if it's worth the purchase